Laser based computer controlled dental preparation system

ABSTRACT

A dental tissue treatment apparatus and associated methods includes a feedback-controlled beam guidance system for directing treatment to a defined area of dental tissue.

RELATED APPLICATIONS

This application claims priority to and benefit of U.S. ProvisionalPatent Application Ser. No. 61/530,761, filed on Sep. 2, 2011, theentire content of which is hereby incorporated by reference in itsentirety.

FIELD OF THE INVENTION

This invention relates generally to the viewing, fluorescing, andscanning of electromagnetic radiation for the prevention and treatmentof dental hard and soft tissue with a pulsed laser dental treatmentdevice.

BACKGROUND

Dental caries (commonly known as “cavities”) is a chronic infectiousdisease that is extremely difficult to completely eradicate. Tooth decayis caused by the demineralization of the tooth structure primarilyoriginating in the enamel (hard tissue). Dental enamel is a thin layer,typically 1 to 2 mm thick, composed of a crystal-like structure ofcarbonated hydroxyapatite comprising 96% of enamel by weight andapproximately 85% by volume. The balance of enamel, 15% by volume, ismade up of water, protein, and lipid. Tooth decay is the result ofdental acids, created by bacteria metabolizing sugars, which in turnde-mineralize the hydroxyapatite. The bacteria create a biofilm after 24hours, referred to as plaque, which is soft and pliable, but after about10 days the plaque hardens significantly to form dental calculus ortartar.

The majority of tooth decay occurs in the occlusal surface (top surface)and in unexposed areas between teeth. The lingual (back surface) andbuccal (front surface) are relatively smooth compared to the occlusalsurface, and therefore, trap less sugars to be metabolized resulting inrelatively less dental acid and less decay than that in the occclusalsurface and the unexposed areas between teeth. Decay is most likely inareas that cannot be brushed and cleaned easily such as pits andfissures on the occlusal surface, areas under the gums, and contactsurfaces between the teeth.

Nevertheless, there has been a remarkable decline in dental caries overthe last 60 years due to various new detection techniques such asdigital x-rays, 3-D x-rays and fluorescence, prevention techniquesincluding fluoride treatments and sealants, and new or improvedtreatment techniques including higher speed dental drills, smallerstronger burs, various wavelength laser technology, and ultrasoniccleaning equipment.

Detection: Analog x-rays have progressed to digital x-rays, and to conebeam 3-D x-rays, which have a higher resolution than the analog x-raysand are stored digitally while progressively using less and lessradiation. Recently optical fluorescence has also been used to identifythe bacterium that leads to tooth decay. Removing the fluorescingbacteria removes the carious tissue.

Prevention: Various fluoride treatments, new toothpastes, andmouthwashes have been introduced that re-mineralize the enamel,specifically with fluorapatite which has a higher resistance to dentalacids than hydroxyapatite. Additionally flowable composites (commonlycalled epoxies) are referred to as “sealants,” and are added to theocclusal surface to prevent bacteria from getting down into pits andfissures.

Treatment: Dental drills have progressed from motor driven ropemechanisms to compressed air driven devices, and to electrical motordriven devices. The Food and Drug Administration (FDA) has approved fivedifferent laser types at seven different wavelengths for a variety ofdental indications. There are single wavelength dental laser devices,multiple wavelength devices, and q-switched, continuous and pulsed laserproducts. There are various dental laser hand pieces and deliverymechanisms, but all of these laser products are manufactured tomaximally or minimally couple into water. Peak water absorption issought to cut enamel because, as previously stated, water is only a 4%or less constituent by weight, so peak water absorption is required tovaporize water thereby fracturing the enamel, albeit slowly. Minimalwater absorption is sought to cut soft tissue, gums and cheeks, so thatthe blood is cauterized and bleeding is minimized.

Recently a new laser based dental treatment system was developed thatemploys a mid-infrared wavelength laser that couples primarily intohydroxyapatite and partially into water. The advantage of coupling intohydroxyapatite, which constitutes about 96% of hard tissue by weight, isfaster cutting with greater resolution, while partially coupling intowater allows for faster soft tissue cutting while cauterizing avoidingbleeding.

In parallel to the above-described dental technology advances, opticalscanners, or spinning mirrors, have been used in material processingapplications for more than three decades. The advantage of usingscanning mirrors to reposition optical energy is that high accuracypositioning can be achieved while overcoming a minimal amount ofinertia. Low inertia allows the positioning system to accelerate anddecelerate rapidly while maintaining high positional accuracy. Over thelast three decades, various spinning mirror geometries have evolvedcreating smaller, faster movements without compromising accuracy.

Despite these advances, laser-based dental treatment systems faceseveral challenges. One of the most common problems relates to the shapeof the area to be treated. A cavity in a tooth rarely has a regularshape such as a square, circle, or an oval. In order to fully treat theaffected area using previously known methods, the operator typicallytreats a regular-shaped area that encompasses the affected area. This,however, can cause damage to tissue that is within the encompassing areabut that is not affected.

There is yet another problem in treating even a regular-shaped area. Theoperator must be able to hold the hand piece used to direct a laser beamto the treatment area extremely steady and then be able to move itcarefully within a selected area. Laser beams used for treatment aregenerally very powerful, and slight movement of the operator's hand orby the patient can cause the laser beam to be directed to tissue thatdoes not require any treatment and can cause damage thereto.Furthermore, within the selected area, the laser energy must be applieduniformly, i.e., the operator must direct substantially the same amountof energy to each point within the selected treatment area. As theoverall treatment area is typically on the order of a few squarecentimeters or even smaller, manually directing a laser beam to thedesired treatment area is difficult and error prone. Therefore, there isa need for improved systems and methods of laser based dental treatment.

SUMMARY

Various embodiments of the present invention facilitate treatment ofvarious dental infections with high accuracy, causing significantly lesspain by mitigating or avoiding unnecessary treatment of unaffectedareas. This is achieved, in part, by employing a computer-controlledoptical system to direct a laser beam to a selected treatment area. Thetreatment area can be selected as a regular shape and also as a polygonthat approximates the area that is actually affected. Computerizedcontrol of the optical system allows the laser beam to stay within theselected treatment area while simultaneously ensuring that the selectedarea is covered, i.e., the laser energy is directed in a substantiallyuniform manner within the selected treatment area. The energy profile ofthe laser beam at or near the treatment surface can also be controlled,in part, by adjusting the focal point of the laser beam. Selecting asuitable energy profile can further aid in uniformly treating theaffected area.

Accordingly, in one aspect, embodiments of the present invention featurean apparatus for dental tissue treatment, that includes an opticalsystem for directing a laser beam to dental tissue being treated. Theoptical system adjusts an energy profile of the laser beam at a locationin proximity to the dental tissue. The apparatus also includes afeedback-controlled beam guidance system for targeting the laser beamwithin a specified area of a surface of the dental tissue.

In some embodiments, the optical system includes a lens. A focal lengthof the lens can be in a range from about 2 inches to about 15 feet. Theenergy profile may be selectable, e.g., by adjusting the optical systemso as to adjust the focal length. The energy profile may be selectedfrom a top-hat profile, a Gaussian profile, and a doughnut-shapedprofile.

In some embodiments, the feedback-controlled beam guidance systemincludes a mirror; a galvanometer that includes (i) an actuator foradjusting a position of the mirror, and (ii) a sensor for determiningthe position of the mirror. The beam guidance system also includes acontroller for controlling the actuator in a step, in response to thedetermined position of the mirror relative to a desired position of themirror. The feedback-controlled beam guidance system may include twomirrors having axes of rotation disposed at about 90 degrees withrespect to each other. A rate at which the controller moves the actuatormay be in a range of about 10 steps per second to about 100,000 stepsper second. Moving the actuator in one step may cause the laser beam atthe surface of the dental tissue to be displaced in a range of about 2micrometers up to about 15 millimeters.

In some embodiments, the desired position of the mirror is determinedaccording to the specified area of the surface of the dental tissue. Thedesired position of the mirror may be determined according to a tracingpattern of the laser beam on the surface of the dental tissue. Thetracing pattern can be a spiral trace, raster trace, and random trace.The specified area of the surface of the dental tissue is one of atriangle, a square, a rectangle, an oval, a circle, and a polygon. Insome embodiments, the specified area of the surface of the dental tissueis a closed area of a user-defined shape having a perimeter that hasseveral segments. The length of one segment can be in a range from about2 μm up to about 15 mm. The specified area of the surface of the dentaltissue may in a range of about 4 μm² up to about 2.25 cm². As such, thespecified area may approximate the affected area.

In some embodiments, the apparatus also includes a hand-held unit havinga tip that can be disposed adjacent to the dental tissue being treated.In addition, the apparatus includes a housing containing the opticalsystem and the beam guidance system. The hand-held unit can be attachedto the housing, whereby the laser beam is activated only if thehand-held unit is attached to the housing. The apparatus may alsoinclude a turning optic disposed within the hand-held unit.

In some embodiments, the apparatus includes an illumination system forilluminating at least a portion of the specified area of the surface ofthe dental tissue. The illumination system includes a light source andan optical system for directing and optionally collimating theilluminating light. The optical system may be adapted for focusing thelight, in addition to directing and optionally collimating the light. Insome embodiments, the illumination system includes a light source and acollector for reflecting light emitted by the light source, and anoptical system for directing and optionally collimating the illuminationlight.

In some embodiments, the apparatus includes a cleansing system containedin the hand-held unit. The cleansing system may include water and/or airsupply. The laser beam used for treatment may be a CO₂ laser beam. TheCO₂ laser beam may have a spot size in range from about 0.03 μm up toabout 0.2 cm. The apparatus may also include a marking laser beam, andthe marking laser beam can be obtained from a gas or a laser diode inthe range of about 500 nm up to about 700 nm, such as a red or greenHe—Ne laser beam.

In some embodiments, the apparatus includes vision system. The visionsystem includes an imaging system and a transfer lens. The imagingsystem may also include an optical filter and/ or a variable focusinglens system. The apparatus may also include a shroud configured to bepositioned inside a person's mouth. In some embodiments, the apparatusincludes an air path for forming an air curtain to effectively stop anyforeign substance from entering the apparatus.

In another aspect, embodiments of the present invention feature a methodfor dental tissue treatment. The method includes directing a laser beamtoward dental tissue being treated, such that the laser beam has acertain energy profile at a location in proximity to the dental tissue.The method also includes targeting the laser beam within a specifiedarea of a surface of the dental tissue via a feedback-controlled beamguidance system. The directing step may be performed using a lens havinga focal length in a range from about 2 inches to about 15 feet. Theenergy profile may be selectable and can be one of a top-hat profile, aGaussian profile, and a doughnut-shaped profile.

In some embodiments, the targeting step includes reflecting the laserbeam using a mirror and determining a position of the mirror. The methodalso includes comparing the determined position of the mirror with adesired position of the mirror, and controlling the position of themirror according to the comparison of the determined and desiredpositions of the mirror. Each of the reflecting, determining, comparing,and adjusting steps may be repeated at a rate in the range of about 10steps per second to about 100,000 steps per second. The reflecting stepmay include reflecting the laser beam using two mirrors having axes ofrotation disposed at about 90 degrees with respect to each other.

In some embodiments, the method also includes determining the desiredposition of the mirror according to the specified area of the surface ofthe dental tissue. The desired position of the mirror may be determinedaccording to a tracing pattern of the laser beam on the surface of thedental tissue. The tracing pattern can be one of a spiral trace, rastertrace, and random trace. The treatment method may also includespecifying a shape, size, or both of the specified area of the surfaceof the dental tissue. The area of the surface of the dental tissue maybe identified by specifying a closed area of a user-defined shape havinga perimeter having several segments. A direction of the laser may bemodified beam using a turning optic.

In some embodiments, the treatment method includes illuminating at leasta portion of the specified area of the surface of the dental tissue. Thelaser beam can be a CO₂ laser beam, and the treatment method may includeablating the dental tissue. The ablated tissue can be soft tissue, hardtissue, or both. In some embodiments, prior to the ablating step, thespecified area of a surface of the dental tissue is marked using a gasor laser diode in the range of about 500 nm up to about 700 nm, such asa red or green He—Ne laser beam.

In some embodiments, the directing step includes focusing the laser beamsuch that a focal point of the focused laser beam is locatedsubstantially at a surface of the dental tissue. The focal point of thefocused laser beam may also be in proximity of a surface of the dentaltissue. For example, the focal point can be above the surface of thedental tissue, or below the surface of the dental tissue.

These and other objects, along with advantages and features of theembodiments of the present invention herein disclosed, will become moreapparent through reference to the following description, theaccompanying drawings, and the claims. Furthermore, it is to beunderstood that the features of the various embodiments described hereinare not mutually exclusive and can exist in various combinations andpermutations. As used herein, the term “substantially” means ±10% and,in some embodiments, ±5%.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. Also, the drawings are notnecessarily to scale, emphasis instead generally being placed uponillustrating the principles of the invention. In the followingdescription, various embodiments of the present invention are describedwith reference to the following drawings, in which:

FIG. 1 shows a cross-section of a typical dental hand-piece according toone embodiment of the invention for dental viewing, diagnosis, andtreatment by means of a laser;

FIG. 2 shows the tip of the hand-piece depicted in FIG. 1 and focusingof the laser beam according to one embodiment of the invention;

FIG. 3 shows some exemplary beam diameters versus energy distributionprofiles across the focused beam diameters;

FIG. 4 shows a closed loop position control system includinggalvanometers and mirrors according to one embodiment of the invention;

FIG. 5 shows a remote illumination system according to one embodiment ofthe invention;

FIG. 6 shows some exemplary laser treatment areas and tracing patterns;and

FIG. 7 shows various parameters of the laser system and the ranges ofthe parameters.

DESCRIPTION

An electromagnetic energy output device is disclosed for implementingprocedures on hard tissue, soft tissue and osseous bone. Theelectro-magnetic energy level and rate output from the device can betailored to the different dental procedures of cutting or ablating soft,hard or osseous tissue, and also for decontamination, cleaningperiodontal pockets, pain reduction, and bio stimulation procedures. SeePCT/US2010/043968 and PCT/US2011/023483 for high power treatment laserssuitable for use herewith, the disclosures of which are incorporated byreference herein in their entirety.

As depicted in FIG. 1, a high power treatment laser beam, such as a CO₂laser beam, enters a dental hand-piece 1 on optical axis 2. The laserbeam is directed through a focusing lens 3 and two computer controlledmoving optical elements 4, 5. The focusing lens 3 may be located aheadof or behind the optical elements 4, 5. An image system may beintegrated into the dental hand-piece 1, and the image system mayinclude an imaging device 6 such as a CMOS or CCD camera chip, a lenssystem 7, a filter 8 and/or a focusing element such as an electro-staticlens 9. The lens system 7 can include a transfer lens and/or a variablefocus lens. The variable focus lens can be used to select a suitableenergy profile of the laser beam, as described below. The imaging systemmay be located co-linearly with the optical axis 2 of the high powertreatment laser beam by reflecting light rays received from thetreatment area and traveling generally along the optical axis 2 off amirror 10 or a mirror 11 coupled to the moving optical elements 4 or 5,respectively.

Regardless the location of the imaging system, the components thereofare configured such that light corresponding to the images of the areaof the dental tissue being treated propagates substantially along theoptical axis 2. As a result, an operator of the laser beam can view thereceived images during treatment, without having to replace thetreatment device with a separate imaging device or without having toposition simultaneously two devices in the patients mouth—one fortreatment and the other for imaging. Moreover, the operator hassubstantially the same perspective as that of the treatment laser beam.This allows the operator to accurately monitor the effect of the laserbeam precisely on the area of the dental tissue being treated duringsuch treatment. This arrangement can also provide comfort to thepatient, because the patient need not open his or her jaw so wide as toallow one access path for the treatment laser beam to the dental tissueand another viewing path, at a different angle, to the operator.

In some embodiments, an optical fluorescence system is integrated intothe dental hand-piece 1. The fluorescence system generally includes anfluorescing light source (e.g., source of ultra-violet (UV) light) thatis located similarly as the imaging device 6. The fluorescence systemmay use one or more of a lens system, filter, and a focusing elementsuch that rays of substantially monochromatic light from the fluorescingsource travel along the optical axis 2 to the dental region to beexamined. If a certain area within that dental region is affected, e.g.,due the presence of bacteria, the light reflected from that areatypically has a peak wavelength different than that of the substantiallymonochromatic light. Those reflected light rays travel back along theoptical axis 2 and may be viewed using the imaging system. The operatorcan analyze the received images to detect any affected areas requiringtreatment.

FIG. 1 also depicts an optical element 12 that turns or reorients theoptical axis 2 so as to increase the ergonometric design of thehand-piece 1. The optical element 12 is optional, however, andembodiments in which the optical axis 2 is not turned at about 90degrees, as shown in FIG. 1, are within the scope of the invention. Ashroud or cover 13 may be added to the hand-piece 1 to position thehand-piece, block the illuminating light (described below), and/or toprevent the treatment laser beam from reaching the dental tissuesubstantially outside the area to be treated. The shroud 13 may alsosupport the dental hand-piece 1 when it is positioned in a patient'smouth.

In some embodiments, illumination diodes or diode lasers 14 are added tothe hand-piece 1 to aid the imaging system, for example, by shininglight in the viewing the area of the dental tissue being treated.Various light collection and focusing elements 15 (e.g., Fresnel lenses)may be used for collecting and guiding the light through the end openingof the hand-piece shroud 13 onto the dental tissue. In some embodiments,a marking laser 16 (described below in detail) is provided to providevisible light where the invisible treatment laser beam will be directed.The marking laser beam also travels along the high power treatment laseraxis 2.

In some embodiments, the imaging system, the illumination system, thecomputer controlled optical elements 4, 5, and the focusing lens 3 arelocated in a housing, and the hand-piece 1 can be attached to thehousing. If the hand-piece 1 is detached from the housing, the laserbeam 50 turns off, thereby preventing accidental exposure to the laserbeam.

With reference to FIG. 2, air and water paths 17, 18 are included in thehand-piece 1. The air and water paths 17, 18 are both optional. Usingthese paths, air, water, or a mixture thereof can be used to spray,clean, or dry the tooth before, during, and/or after treatment. The airand water mixture can create a water mist that generally aids in cuttingof hard dental tissue by providing cooling. Air alone may be used to cutsoft dental tissue or to dry or blow off dental tissue. An additionalair path 19 is optionally added to provide an air flow near the openingof the hand-piece tip/shroud 13. The air path 19 creates a curtain ofpressurized air across the opening in tip/shroud 13, blocking any waterused in treatment and/or debris resulting from cutting from enteringinto the hand-piece and attaching to the mirror 12.

In the end portion of dental laser hand-piece 1, the high powertreatment laser beam 50 reflects off the mirror 12 and focuses at apoint of focus 21. Using a converging laser beam 50, a substantiallyflat mirror 12 can be used to focus the laser beam at or near the point21. Alternatively or in addition, a multi-segment mirror or a concavemirror can be used to focus parallel or converging laser beams at thepoint of focus 21.

The location 21 at which the laser beam focuses, i.e., the laser beam'scutting depth with respect to the dental tissue 51, can be adjusted overa range “X” 22. Though FIG. 2 shows the point of focus 21 of the laserbeam slightly above the surface 51 of the dental tissue, the point offocus 21 can be located at or below the surface 51. Adjusting the pointof focus 21 of the laser beam at a distance from the surface 51 (i.e.,above or below the surface 51) facilitates varying the energy densityprofile of the laser beam at the treatment surface 51. Thus, byadjusting the location of the point of focus 21, a laser of a suitableenergy profile can be directed to the treatment area on the dentaltissue surface 51.

As depicted in FIG. 3, various energy distribution profiles can begenerated at the treatment surface 51. In some embodiments, using aspherical optic a Gaussian energy distribution 24 is achieved and usingnon-spherical optics various other energy distributions such as adonut-shaped 25 distribution or a Top Hat 26 distribution can beachieved. Using different energy distribution profiles, accuracy oftreatment can be improved. For example, the Gaussian profile 24 can beused to treat a relatively small affected area, while the Top Hatprofile 26 can be used to treat a relatively large affected area.Moreover, using the Top Hat profile 26, laser energy can be directedmore uniformly across a relatively large area, as opposed to applyingsignificant amount of energy only to the center of the treatment area ifan energy profile having a peak (such as the Gaussian profile 24) wereused.

With reference to FIG. 4, the high power treatment laser beam 50 passesthrough the focusing lens 3 and the focused beam is directed by spinningmirrors 27, 28. The spinning mirrors 27, 28 are computer controlledmoving optical elements 4, 5 shown in FIG. 1 The spinning mirrors 27, 28can be moved in steps such that the point of focus 21 of the treatmentlaser beam 50 can be moved along X and/or Y directions so as to coversubstantially entirely a treatment area 29. The spinning mirrors 27, 28can be controlled by a positional closed loop feedback system thatincludes motors 30, 31. The motors 30, 31 typically include agalvanometer including an actuator for adjusting positions of thespinning mirrors 27, 28. The positional loop associated with the motor30 includes a sensor or position indicator 34, an electronic positioncontrol device 32, and the motor drive electronics 33. A secondpositional control loop (not shown), which may utilize one or more ofthe components 32-34, is associated with the motor 31.

Though FIG. 4 shows the dental tissue treatment area 29 as having asquare shape, this is for illustrative purposes only. It should beunderstood that other shapes such as a triangle, polygon, circle, oval,etc., are within the scope of the invention. As explained in detail withreference to FIG. 6 below, in some embodiments, the treatment area 29can be defined by the operator. The position control device 32 isprovided with information about the treatment area 29. Such informationmay include the size and shape of the treatment area 29. The positionindicator 34 determines the relative position of the point of focus 21of the laser beam 50 within the treatment area 29 at a particularinstance. Based on the relative position obtained from the positionindicator 34, the position control device 32 can determine the movementof the motor 30 during the next step of operation. These steps aredetermined for each of the motors 30, 31 such that the laser beam 50 issubstantially confined to the treatment area 29, and covers, i.e.,treats the area 29 in a substantially uniform manner. Thus, thepositional closed-loop feedback system enables an operator to selectand/or define a treatment area that approximates only the affected areaof an irregular shape, and to automatically treat the entire selectedand/or defined area, without substantially affecting the other portionsof the unaffected dental tissue adjacent to the treatment area.

With reference to FIG. 5, light rays from the LED or laser diode lightelements 14 are reflected by a collector 36 and can be collimated orfocused by an optical element 15. The collimated/focused light rays arereflected off the dental hand-piece turning mirror 12 to the focusposition 21, i.e., the point of focus of the high power treatment laserbeam 50, as described above with reference to FIGS. 2 and 4. TheLED/laser diode elements 14 can be mounted in the hand-piece 1 on aprinted circuit board 37, for example. The focusing elements 15 can beformed using, for example, an optic 38 having lenslets 39, or a Fresnellens 40. Alternatively or in addition, the light from the elements 14can reflect off a polished interior of the hand-piece 1, so as to beguided to the treatment area through the opening in the tip/shroud 13 ofthe hand-piece 1.

As depicted in FIG. 6, the treatment area 29 treated by the laser beam50 that is moved using the two spinning mirrors 27, 28 as describedabove with reference to FIG. 4, can be a polygon 42 (i.e., a triangle,square, rectangle, hexagon, etc.), a circle or oval, or any operatordefined shape 43. A user/operator may define the shape 43 as a closedarea having a perimeter of short segments of length in the range about12 μm to about 1.5 cm. In contrast to treating dental tissue areas of afixed size and/or shape, such as a 4 mm×4 mm square, defining the shape43 as a polygon of short segments enables the operator to preciselyselect virtually only the affected area of the dental tissue fortreatment. As described above with reference to FIG. 4, substantiallyonly the selected, i.e., affected, area can be treated by the laserbeam, without unnecessarily exposing the adjacent unaffected tissue tothe laser beam radiation.

During treatment, the mirrors 27, 28 and the associated positionalcontrol loops (shown in FIG. 4) are configured such that the laserpulses or a continuous power electromagnetic energy of the laser beamtraces the entire treatment area 42 or 43 according to a pattern. Asshown in FIG. 6, the tracing pattern can be a spiral pattern 41, araster pattern, or a random pattern 44. When a laser beam impinges upona spot in the treatment area 42 or 43, a plume of tissue material may beemitted. During the next step, moving the laser beam to a randomlyselected location, as shown by the pattern 44, can avoid any interactionbetween the treatment laser beam and the plume, and, instead, the laserbeam is directed to the tissue to be treated.

Prior to commencing treatment using the treatment laser beam asdescribed above, it may be beneficial for an operator to ensure that thetreatment laser beam would, in fact, impinge upon all of the treatmentarea in a uniform manner, and not impinge upon the tissue not to betreated. To this end, the marking laser 16 described above withreference to FIG. 1 can be used. The marking laser 16, e.g., a He—Nelaser, traces the treatment area 42 or 43 substantially similarly as thetreatment laser beam would, because both laser beams are focused alongthe axis 2, and both laser beams are directed using the systemschematically shown in FIG. 4. The marking laser 16, however, lackspower to ablate or adversely affect dental tissue in the area 42 or 43,and, hence, may not inadvertently damage the dental tissue within oradjacent to the treatment area 42 or 43.

Moreover, the marking laser 16 emits visible light, such as red light,so that the operator can see the tracing of the area 42 or 43 as themarking laser beam is moved, using the imaging system described abovewith reference to FIG. 1. Once the operator ensures that the markinglaser 16 covers substantially the entire treatment area according to theselected tracing pattern (e.g., patterns 41, 44), and does not affectareas substantially outside the treatment area 42 or 43, the operatorcan activate the treatment laser beam, and treat the area, as describedabove. Using the marking laser 16 in combination with thecomputer-controlled feedback system to control the movement of laserbeam, only the affected dental areas of virtually any size and shape canbe treated effectively and easily, while mitigating or eliminating therisk of significant damage to the surrounding unaffected areas.

FIG. 7 shows a table identifying various system parameters such asenergy densities, pulse width of the laser beam, length of a segmentused to define a treatment area, etc. The ranges of the parameters, andtheir nominal values are also shown in the table.

While the invention has been particularly shown and described withreference to specific embodiments, it will be understood by thoseskilled in the art that various changes in form and detail may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims. The scope of the invention is thusindicated by the appended claims and all changes that come within themeaning and range of equivalency of the claims are therefore intended tobe embraced.

1. An apparatus for dental tissue treatment, the apparatus comprising:an optical system for directing a laser beam to dental tissue beingtreated, whereby the laser beam has an energy profile at a location inproximity to the dental tissue; and a feedback-controlled beam guidancesystem for targeting the laser beam within a specified area of a surfaceof the dental tissue.
 2. The apparatus of claim 1, wherein the opticalsystem comprises a lens.
 3. The apparatus of claim 2, wherein a focallength of the lens is in a range from about 2 inches to about 15 feet.4. The apparatus of claim 1, wherein the energy profile is selectableand is selected from the group consisting of a top-hat profile, aGaussian profile, and a doughnut-shaped profile.
 5. The apparatus ofclaim 1, wherein the feedback-controlled beam guidance system comprises:a mirror; a galvanometer comprising (i) an actuator for adjusting aposition of the mirror, and (ii) a sensor for determining the positionof the mirror; and a controller for controlling the actuator in a step,in response to the determined position of the mirror relative to adesired position of the mirror.
 6. The apparatus of claim 5, wherein thefeedback-controlled beam guidance system comprises two mirrors havingaxes of rotation disposed at about 90 degrees with respect to eachother.
 7. The apparatus of claim 5, wherein a rate at which thecontroller moves the actuator is in a range of about 10 steps per secondto about 100,000 steps per second.
 8. The apparatus of claim 5, whereinmoving the actuator in one step causes the laser beam at the surface ofthe dental tissue to be displaced in a range of about 2 micrometers upto about 15 millimeters.
 9. The apparatus of claim 5, wherein thedesired position of the mirror is determined according to the specifiedarea of the surface of the dental tissue.
 10. The apparatus of claim 9,wherein the desired position of the mirror is determined according to atracing pattern of the laser beam on the surface of the dental tissue,the tracing pattern being selected from the group consisting of spiraltrace, raster trace, and random trace.
 11. The apparatus of claim 1,wherein the specified area of the surface of the dental tissue is one ofa triangle, a square, a rectangle, an oval, a circle, and a polygon. 12.The apparatus of claim 1, wherein the specified area of the surface ofthe dental tissue is a closed area of a user-defined shape having aperimeter comprising a plurality of segments.
 13. The apparatus of claim12, wherein a length of one segment is in a range from about 2 μm up toabout 15 mm.
 14. The apparatus of claim 1, wherein the specified area ofthe surface of the dental tissue is in a range of about 4 μm² up toabout 2.25 cm².
 15. The apparatus of claim 1, further comprising: ahand-held unit having a tip disposable adjacent to the dental tissuebeing treated; and a housing containing the optical system and the beamguidance system, the hand-held unit being attachable to the housing,whereby the laser beam is activated only if the hand-held unit isattached to the housing.
 16. The apparatus of claim 15, furthercomprising a turning optic disposed within the hand-held unit.
 17. Theapparatus of claim 15, further comprising an illumination system forilluminating at least a portion of the specified area of the surface ofthe dental tissue, the illumination system comprising: a light sourceand an optical system for directing the illuminating light.
 18. Theapparatus of claim 15, further comprising an illumination system forilluminating at least a portion of the specified area of the surface ofthe dental tissue, the illumination system comprising: a light sourceand an optical system for directing, collimating, and focusingilluminating light.
 19. The apparatus of claim 15, further comprising anillumination system for illuminating at least a portion of the specifiedarea of the surface of the dental tissue, the illumination systemcomprising: a light source and a collector for reflecting light emittedby the light source; and an optical system for directing theilluminating light.
 20. The apparatus of claim 15, further comprising acleansing system contained in the hand-held unit.
 21. The apparatus ofclaim 1, wherein the laser beam is a CO₂ laser beam.
 22. The apparatusof claim 21, wherein CO₂ laser beam has a spot size in range from about0.03 μm up to about 0.2 cm.
 23. The apparatus of claim 1, furthercomprising a marking laser beam.
 24. The apparatus of claim 25, whereinthe marking laser beam obtained from a gas or diode laser in the rangeof about 500 nm up to about 700 nm.
 25. The apparatus of claim 1,further comprising a vision system comprising: an imaging system and atransfer lens;
 26. The apparatus of claim 25, further comprising anoptical filter.
 27. The apparatus of claim 25, further comprising avariable focusing lens system.
 28. The apparatus of claim 25, furthercomprising an optical filter and a variable focusing lens system. 29.The apparatus of claim 1, further comprising a shroud configured to bepositioned inside a person's mouth.
 30. The apparatus of claim 1,further comprising an air path for forming an air curtain to stop anyforeign substance from entering the apparatus.
 31. A method for dentaltissue treatment, comprising: directing a laser beam toward dentaltissue being treated, whereby the laser beam has an energy profile at alocation in proximity to the dental tissue; and targeting the laser beamwithin a specified area of a surface of the dental tissue via afeedback-controlled beam guidance system.
 32. The method of claim 31,wherein the directing step is performed using a lens having a focallength in a range from about 2 inches to about 15 feet.
 33. The methodof claim 31, wherein the energy profile is selectable and is selectedfrom the group consisting of a top-hat profile, a Gaussian profile, anda doughnut-shaped profile.
 34. The method of claim 31, wherein thetargeting step comprises: reflecting the laser beam using a mirror;determining a position of the mirror; comparing the determined positionof the mirror with a desired position of the mirror; and controlling theposition of the mirror according to the comparison of the determined anddesired positions of the mirror.
 35. The method of claim 34, whereineach of the reflecting, determining, comparing, and adjusting steps isrepeated at a rate in the range of about 10 steps per second to about100,000 steps per second.
 36. The method of claim 34, wherein thereflecting step comprises reflecting the laser beam using two mirrorshaving axes of rotation disposed at about 90 degrees with respect toeach other.
 37. The method of claim 34, further comprising determiningthe desired position of the mirror according to the specified area ofthe surface of the dental tissue.
 38. The method of claim 37, whereinthe desired position of the mirror is determined according to a tracingpattern of the laser beam on the surface of the dental tissue, thetracing pattern being selected from the group consisting of spiraltrace, raster trace, and random trace.
 39. The method of claim 34,further comprising specifying a shape of the specified area of thesurface of the dental tissue.
 40. The method of claim 34, furthercomprising specifying a size of the specified area of the surface of thedental tissue.
 41. The method of claim 34, further comprising specifyingthe specified area of the surface of the dental tissue by specifying aclosed area of a user-defined shape having a perimeter comprising aplurality of segments.
 42. The method of claim 31, further comprisingmodifying a direction of the laser beam using a turning optic.
 43. Themethod of claim 31, further comprising illuminating at least a portionof the specified area of the surface of the dental tissue.
 44. Themethod of claim 31, wherein the laser beam is a CO₂ laser beam, and themethod comprises ablating the dental tissue.
 45. The method of claim 44,wherein the ablated tissue comprises at least one of soft tissue andhard tissue.
 46. The method of claim 44, further comprising, prior tothe ablating step, marking the specified area of a surface of the dentaltissue using a red or green laser beam in the range of about 500 nm upto about 700 nm.
 47. The method of claim 31, wherein the directingcomprises focusing the laser beam such that a focal point of the focusedlaser beam is located substantially at a surface of the dental tissue.48. The method of claim 31, wherein the directing comprises focusing thelaser beam such that a focal point of the focused laser beam is inproximity of a surface of the dental tissue.
 49. The method of claim 48,wherein the focal point is above the surface of the dental tissue. 50.The method of claim 48, wherein the focal point is below the surface ofthe dental tissue.